From: Ben Creisler
bcreisler@gmail.com
A new paper in PLoS ONE:
Anthony R. Fiorillo & Ronald S. Tykoski (2013)
An Immature Pachyrhinosaurus perotorum (Dinosauria: Ceratopsidae)
Nasal Reveals Unexpected Complexity of Craniofacial Ontogeny and
Integument in Pachyrhinosaurus.
PLoS ONE 8(6): e65802.
doi:10.1371/journal.pone.0065802
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0065802
A new specimen attributable to an immature individual of
Pachyrhinosaurus perotorum (Dinosauria, Ceratopsidae) from the
Kikak-Tegoseak Quarry in northern Alaska preserves a mix of features
that provides refinement to the sequence of ontogenetic stages and
transformations inferred for the development of the nasal boss in
Pachyrhinosaurus. The new specimen consists of an incomplete nasal
that includes the posterior part of the nasal horn, the dorsal surface
between the horn and the left-side contacts for the prefrontal and
frontal, and some of the left side of the rostrum posteroventral to
the nasal horn. The combination of morphologies in the new specimen
suggests either an additional stage of development should be
recognized in the ontogeny of the nasal boss of Pachyrhinosaurus, or
that the ontogenetic pathway of nasal boss development in P. perotorum
was notably different from that of P. lakustai. Additionally, the
presence of a distinct basal sulcus and the lateral palisade texture
on the nasal horn of the specimen described here indicate that a
thick, cornified horn sheath was present well before the formation of
a dorsal cornified pad. A separate rugose patch on the nasal well
posterior to the nasal horn is evidence for a cornified integumentary
structure, most likely a thick cornified pad, on the posterior part of
the nasal separate from the nasal horn prior to the onset of nasal
boss formation in P. perotorum.